Abstract:

A novel evaluation index is introduced so as to allow both a total
evaluation of data recording and an evaluation of individual detection
patterns. A data recording evaluation method includes a step of
reproducing the result of data recording performed on an optical disk and
identifying a predetermined detection pattern in a reproduction signal, a
step of detecting the signal state of the reproduction signal
corresponding to the predetermined detection pattern, and a first
calculation step of calculating a first recording state evaluation index
value based on the detected signal state and a reference condition which
is identified from the predetermined detection pattern and adjusted so as
to reflect the signal state of the reproduction signal. When there is a
plurality of predetermined detection patterns, the method further
includes a second calculation step of calculating a second recording
state evaluation index value using the first recording state evaluation
index value for each of the predetermined detection patterns. Data
recording can be evaluated properly using the first and second recording
state evaluation index values.

Claims:

1-27. (canceled)

28. A method of data recording, comprising:reproducing a result of data
recording on an optical disk and identifying a detection pattern p of
which an occurrence frequency in a reproduction signal is equal to or
greater than a predetermined value;measuring a signal value D(x) in the
reproduction signal corresponding to said detection pattern p;calculating
a first recording state evaluation index value PRerror_ptn(p) using the
measured signal value D(x) in the reproduction signal and a value R(x) of
a reference signal corresponding to the detection pattern p in accordance
with Equation 1: PRerror_ptn ( p ) = { x = a a + n - 1
( D ( x ) - R ( x ) ) 2 } / n , ##EQU00003##
where a is a predetermined data number at a start of processing, n is the
number of predetermined data sampling, and x is a variable representing
data sampling points;calculating a second recording state evaluation
index value PRerror_ttl using said first recording state evaluation index
value and an occurrence probability for each of a plurality of the
detection patterns p in accordance with Equation 2: PRerror_ttl = p
PRerror_ptn ( p ) * Occurrence probability ( p
) ; ##EQU00004## judging whether or not the second recording state
evaluation index value PRerror_ttl has exceeded a predetermined
threshold;identifying a detection pattern p that has a predetermined
influence level or greater influence level on said second recording state
evaluation index value based on the corresponding first recording state
evaluation index value when the second recording state evaluation index
value has exceeded the predetermined threshold, the detection pattern p
being a pattern including at least one mark and space;calculating a
difference between the measured signal value D(x) in the reproduction
signal and the value R(x) of the reference signal corresponding to said
identified detection pattern p; andcalculating a correction amount for a
recording parameter separately depending on whether the calculated
difference is positive or negative.

29. A recording and reproduction device for optical disk comprising:means
for reproducing a result of data recording on an optical disk and
identifying a detection pattern p of which an occurrence frequency in a
reproduction signal is equal to or greater than a predetermined
value;means for measuring a signal value D(x) in the reproduction signal
corresponding to said detection pattern p;means for calculating a first
recording state evaluation index value PRerror_ptn(p) using the measured
signal value D(x) in the reproduction signal and a value R(x) of a
reference signal corresponding to the detection pattern p in accordance
with Equation 1: PRerror_ptn ( p ) = { x = a a + n - 1
( D ( x ) - R ( x ) ) 2 } / n , ##EQU00005##
where a is a predetermined data number at a start of processing, n is the
number of predetermined data sampling, and x is a variable representing
data sampling points;means for calculating a second recording state
evaluation index value PRerror_ttl using said first recording state
evaluation index value and an occurrence probability for each of a
plurality of the detection patterns p in accordance with Equation 2:
PRerror_ttl = p PRerror_ptn ( p ) * Occurrence
probability ( p ) ; ##EQU00006## means for judging whether or
not the second recording state evaluation index value PRerror_ttl has
exceeded a predetermined threshold;means for identifying a detection
pattern p that has a predetermined influence level or greater influence
level on said second recording state evaluation index value based on the
corresponding first recording state evaluation index value when the
second recording state evaluation index value has exceeded the
predetermined threshold, the detection pattern p being a pattern
including at least one mark and space;means for calculating a difference
between the measured signal value D(x) in the reproduction signal and the
value R(x) of the reference signal corresponding to said identified
detection pattern p; andmeans for calculating a correction amount for a
recording parameter separately depending on whether the calculated
difference is positive or negative.

30. An optical recording information medium having data recorded therein,
the data representing a relationship among a first recording state
evaluation index value PRerror_ptn(p), a second recording state
evaluation index value PRerror_ttl, and a correction amount for a
recording parameter,wherein said first recording state evaluation index
value PRerror_ptn(p) is calculated by:reproducing a result of data
recording on an optical disk and identifying a detection pattern p of
which an occurrence frequency in a reproduction signal is equal to or
greater than a predetermined value;measuring a signal value D(x) in the
reproduction signal corresponding to said detection pattern p;
andcalculating a first recording state evaluation index value
PRerror_ptn(p) using the measured signal value D(x) in the reproduction
signal and a value R(x) of a reference signal corresponding to the
detection pattern p in accordance with Equation 1: PRerror_ptn ( p )
= { x = a a + n - 1 ( D ( x ) - R ( x )
) 2 } / n , ##EQU00007## where a is a predetermined data number
at a start of processing, n is the number of predetermined data sampling,
and x is a variable representing data sampling points,wherein said second
recording state evaluation index value PRerror_ttl is calculated using
said first recording state evaluation index value and an occurrence
probability for each of a plurality of the detection patterns p in
accordance with Equation 2: PRerror_ttl = p PRerror_ptn (
p ) * Occurrence probability ( p ) , ##EQU00008##
andwherein said correction amount for the recording parameter is
calculated by:judging whether or not the second recording state
evaluation index value PRerror_ttl has exceeded a predetermined
threshold;identifying a detection pattern p that has a predetermined
influence level or greater influence level on said second recording state
evaluation index value based on the corresponding first recording state
evaluation index value when the second recording state evaluation index
value has exceeded the predetermined threshold, the detection pattern p
being a pattern including at least one mark and space;calculating a
difference between the measured signal value D(x) in the reproduction
signal and the value R(x) of the reference signal corresponding to said
identified detection pattern p; andcalculating the correction amount for
the recording parameter separately depending on whether the calculated
difference is positive or negative.

31. A recoding medium storing a program executable by a processor, the
program causing the processor to execute the method of data recording as
claimed in claim 28.

32. A processor including a memory storing a program executable by the
processor, the program causing the processor to execute the method of
data recording as claimed in claim 28.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a technique for evaluation of data
recording on an optical disk.

BACKGROUND ART

[0002]In recent years, with the advent of high-definition TV, digital
images or the like can be recorded with high density and for a longer
period. As an optical recording information medium meeting this demand,
an optical recording information medium (hereinafter referred to as an
"optical disk"), such as a write-once type HD-DVD (hereinafter referred
to as "HD-DVD-R") or a write-once type Blue-ray disc (hereinafter
referred to as "BD-R"), has been developed. This optical disk has a
structure in which a recording layer, a reflective layer, and a
protective layer are formed on one principal surface of an optical
transparency disk substrate. Moreover, spiral or concentric-circle
grooves are formed on the surface of the substrate on which the recording
layer and the reflective layer are formed, and a portion between adjacent
grooves is formed to be a convex portion called a land. In such an
optical disk, recording is performed by irradiating the recording layer
over the grooves with a recording laser beam so as to cause the beam to
track along the grooves using a recording and reproduction device for
optical disk and forming recording pits (hereinafter referred to as
"marks") on the recording layer so as to be replaced with symbols.
Reproduction is performed by irradiating an array formed by such marks
having a length nT (T is a bit length between reference channel clocks,
and nT is an integral multiple of n of the bit length) and portions
having a length of nT (hereinafter referred to as "spaces") between the
marks with a laser beam for reproduction and converting reflected light
into symbols of a reproduction signal.

[0003]In the optical disk, a high recording density type optical disk
system such as the HD-DVD standard or the Blue-ray disk standard
(hereinafter referred to as "BD standard") is established. The important
demands in these high recording density techniques are higher recording
capacity and faster signal processing. Meeting these demands causes
another problem. The problem concerns the SN ratio and the inter-symbol
interference. This problem takes place because the beam diameter of a
laser beam for reading is larger than the size of isolated pits when
reading recorded pits using an optical head. To solve these problems, a
signal processing method called partial response maximum likelihood
(hereinafter simply referred to as "PRML") is proposed which is
appropriate for reproduction of high recording density information. The
PRML method is a method in which the characteristics of partial response
(simply referred to as "PR"), which is a reproduction technique based on
the presumption that inter-symbol interference is present, are combined
with a maximum likelihood (hereinafter simply referred to as "ML")
technique which selectively combines the most probable signal series
among reproduction signals. Further, the PRML method is to perform
reproduction using energy of a signal voltage at channel clock positions
of adjacent signals without performing excessive waveform equalization in
order to remove inter-symbol interference. In such a PRML technique,
various techniques for evaluating data recording and optimizing the
recording conditions and reproduction conditions based on the evaluation
results are proposed.

[0004]For example, JP-A-2003-151219 discloses a technique relating to the
evaluation of quality of a reproduction signal. Specifically, the
technique utilizes a predetermined reproduction signal, a first pattern,
which corresponds to a signal waveform pattern of the reproduction
signal, and an arbitrary pattern (a second or third pattern), which is
different from the first pattern and which corresponds to the signal
waveform pattern of the reproduction signal. First, a difference D=Ee-Eo
between a distance Eo between the reproduction signal and the first
pattern and a distance Ee between the reproduction signal and the
arbitrary pattern is calculated. Subsequently, a distribution of such
distance differences D is calculated for a plurality of samples of
reproduction signals. After that, a quality evaluation parameter
(M/σ) for reproduction signals is determined based on the ratio of
the mean M of the calculated distance differences D to the standard
deviation o of the distribution of the calculated distance differences D.
Then, the quality of the reproduction signals is judged from an
evaluation index value (Mgn) represented by the quality evaluation
parameter.

[0005]Moreover, JP-A-2003-141823 discloses a technique for evaluating the
quality of a signal based on an index, which enables the error rate of a
binarization result obtained using maximum likelihood decoding to be
estimated appropriately. Specifically, the technique relates to a maximum
likelihood decoding method in which a most probable state transition path
of a decoded signal is estimated from n (n is an integer of 2 or larger)
state transition paths, in which the decoded signal can have plural
states at arbitrary time point k (k is an arbitrary integer), the decoded
signal transitioning its state in accordance with a state transition rule
such that the decoded signal can transition from a state at time point
k-j (j is an integer of 2 or larger) to the state at time point k along n
state transition paths. If it is assumed that the reliability of the
results of decoding from time point k-j to time point k is |PA-PB| where
PA is the probability of a state transition from the state at time point
k-j to the state at time point k along the most probable state transition
path among the n state transition paths, and PB is the probability of a
state transition from the state at time point k-j to the state at time
point k along the next most probable state transition path among the n
state transition paths, by calculating the value of |PA-PB| for a
predetermined period of time or a predetermined number of times to
calculate a variation thereof, it is possible to obtain an index
indicating the quality of a signal which is correlated with the error
rate of the binarization result obtained using the maximum likelihood
decoding.

[0006]In addition, JP-A-2002-197660 discloses a recording state detection
technique which enables channel-adaptive detection of a recording state
when reproducing information recorded in a high density using a Viterbi
detector. Specifically, after a reproduction signal read from a disk
device is corrected by a band-limiting filter and an equalizer so as to
have specific channel characteristics, the signal is read as a digital
signal xi by an A/D converter in time with a synchronous clock generated
by a PLL circuit. The digital signal xi is input to the Viterbi detector
to obtain a Viterbi detection output signal. The Viterbi detection output
is input to a reference level judgment device and an error margin
calculation circuit. The error margin calculation circuit calculates a
difference Ei between the digital signal xi and the Viterbi
detection output and outputs the difference to a recording state
detecting circuit. The recording state detecting circuit detects the
amplitude or the amplitude level and asymmetry of the difference using an
output from the reference level judgment device and outputs detection
information.

[0007]As a technique relating to a reference signal using maximum
likelihood decoding, JP-A-2005-267759 discloses an invention in which
only the peak and bottom signal levels of each of the shortest symbol (3
T) and the longest symbol (11 T) of a recording bit in an RF reproduction
equalization signal are detected and calculated for each symbol (2 T to
11 T) as Viterbi expectations, and the signals are supplied to a maximum
likelihood decoding circuit, thus executing a branch metric operation.

[0008]Furthermore, a system in which an output signal of a Viterbi
detection circuit is passed through a demultiplexer, and a signal of a
reference level is supplied from an adaptation table to a Viterbi
detector is disclosed in IEEE'2002 paper titled "Adaptive
Partial-Response Maximum-Likelihood Detection in Optical Recording
Media". In this adaptation table, a method of creating a corresponding
reference table for each of 10 kinds of binary signals is described.

[0014]According to recent PRML techniques, a reproduction signal is
equalized to predetermined PR characteristics using a waveform equalizer.
Since it is not possible to obtain optimal characteristics if the
equalized signal is fixed as a reference signal, various techniques are
proposed for variably optimizing the equalized signal so as to follow
changes in an RF reproduction signal (hereinafter referred to simply as
"reproduction signal"). That is, a technique is known which is called
"adaptive PRML" in which a target signal level serving as a reference for
evaluation is changed in accordance with the level of a detected
reproduction signal. In the techniques for evaluating data recording
disclosed in Patent Literature Nos. 1 to 3, an evaluation method
compliant with the adaptive PRML is not disclosed. Moreover, although the
techniques disclosed in Patent Literature 4 and Non-Patent Literature
disclose an evaluation method compliant with the adaptive PRML, an
evaluation of data recording for individual record patterns is not always
appropriately correlated with a total evaluation of data recording.

[0015]It is, therefore, an object of the present invention to provide a
technique in which a novel evaluation index compliant with adaptive PRML
is introduced so as to enable a total evaluation of data recording, thus
reducing reproduction errors.

[0016]Another object of the present invention is to provide a technique in
which a novel evaluation index compliant with adaptive PRML is introduced
so as to enable an appropriate evaluation of individual record patterns,
thus reducing reproduction errors.

[0017]Another object of the present invention is to provide a technique
which complies with adaptive PRML and enables appropriate correlation
between a total evaluation of data recording and an evaluation of data
recording for individual record patterns, thus reducing reproduction
errors.

[0018]Another object of the present invention is to provide a technique in
which recording conditions or recording parameters are appropriately
adjusted based on an evaluation of data recording compliant with adaptive
PRML, thus reducing reproduction errors.

Solutions to Problems

[0019]A method of evaluating data recording according to the present
invention includes the steps of reproducing data recorded on an optical
disk and detecting a predetermined pattern from the reproduced signal;
detecting a signal condition of the reproduced signal that corresponds to
the predetermined pattern; and a first calculation step of calculating a
first recording state evaluation index value--for example, PRerror_ptn(p)
in the disclosed embodiments--based on the detected signal condition and
a reference condition, which is specified by the predetermined pattern
and adjusted to reflect the signal condition.

[0020]By calculating this first recording state evaluation index value, it
is possible to determine whether proper data recording is conducted in a
relation with the reference condition regarding a predetermined pattern.
That is, appropriate evaluation is possible for each of recording
patterns.

[0021]Further, where there is a plurality of the predetermined patterns,
the prevent invention may further include a second calculation step of
calculating a second recording state evaluation index value--for example,
PRerror_ttl in the disclosed embodiments--using the first recording state
evaluation index value for each of the predetermined patterns. By
calculating the second recording state evaluation index value this way,
it is possible to evaluate data recording for a variety of recording
patterns as a whole.

[0022]Further, the present invention may further include a first
modification step of modifying a data recording condition for data
recording--for example, a condition for oscillation directions of the
recording waveforms--based on the second recording state evaluation index
value. This way, it is possible to properly and comprehensively adjust
the recording conditions for data recording based on the second recording
state evaluation index value.

[0023]Furthermore, the second calculation step may include the step of
calculating, for each of the predetermined patterns, a product of an
occurrence probability and the first recording state evaluation index,
and calculating a total sum of each of the calculated products to
calculate the second recording state evaluation index value. This is for
the purpose of putting larger weighting factors to the patterns that
appear more frequently so that the second recording state evaluation
index value reflects their total influences on data recording.

[0024]Further, the present invention may further include the steps of
judging whether or not the second recording state evaluation index value
has exceeded a predetermined threshold; and identifying the predetermined
pattern that has a predetermined or greater influence level on the second
recording state evaluation index value--for example, the one that has a
value exceeding a predetermined value or upper predetermined number of
units--based on the corresponding first recording state evaluation index
value when the second recording state evaluation index value has exceeded
the predetermined threshold. This way, it is possible to identify
problematic patterns.

[0025]Further, the present invention may further include a second
modification step of modifying a recoding parameter used for data
recording--for example, parameters in the time axis direction of the
recording waveform (dTrop2 T, etc.)--based on the first recording state
evaluation index value relating to the identified pattern. This way,
adjustment of recording parameters can be effectively performed.

[0026]Here, the above-mentioned predetermined patterns may be made of at
least one mark and one space.

[0027]Further, the predetermined pattern may be a pattern the occurrence
probability of which exceeds a predetermined value. If the occurrence
probability is very small, such a pattern may be removed from patterns to
be processed in order to reduce the processing load.

[0028]Moreover, the first modification step may include the step of
specifying the recording condition under which the second recording state
evaluation index value assumes the most preferable value, based on a
relation between recording conditions and the second recording state
evaluation index value calculated based on the condition of a signal
obtained by reproduction of data recorded under the recording conditions.
For example, the most preferable recording conditions for data recording
can be specified before start recording data in this way.

[0029]Further, the second modification step may include the step of
calculating a modification amount of the recording condition at a point
in time, using a relation between recording conditions and the second
recording state evaluation index value calculated based on the condition
of a signal obtained by reproduction of data recorded under the recording
conditions and using the second recording state evaluation index value at
the point in time. Thus, in adjusting the recoding conditions during the
data recording, the second recording state evaluation index value can be
used.

[0030]Here, a relation between the recording conditions and the second
recording state evaluation index value calculated based on the condition
of a signal obtained by reproduction of data recorded under the recording
conditions can correspond to data obtained at the time of a test
recording. During a test recording, the second recording state evaluation
index value can be calculated for each of the cases set by varying
recording conditions.

[0031]Further, the second modification step may include the step of
specifying the recording parameter under which the first recording state
evaluation index value assumes a most preferable value, based on a
relation between the recording condition and the first recording state
evaluation index value calculated based on the condition of a signal
obtained by reproduction of data recorded under the recording condition.

[0032]Furthermore, the second modification step may include the step of
calculating a modification amount for the recording parameter at a point
in time, using a relation between the recording parameter and the first
recording state evaluation index value calculated based on the condition
of a signal obtained by reproduction of data recorded with the recording
parameters and using the first recording state evaluation index value at
that point in time.

[0033]Further, a relation between recording parameters and the first
recording state evaluation index value calculated based on the condition
of a signal obtained by reproduction of data recorded with the recording
parameters may correspond to data obtained at a time of a test recording.

[0034]Further, the aforementioned first calculation step may include the
step of calculating the amount of a difference between the detected
signal condition and a reference condition, which is specified by the
predetermined pattern and adjusted to reflect the signal condition. This
way, the present invention can be sufficiently adapted to systems using
the adaptive PRML signal processing method--i.e., systems conforming to
the BD standard or the HD-DVD standard.

[0035]Further, the aforementioned first calculation step may include the
step of setting each level of target levels based on the signal condition
of the reproduced signal; the step of adjusting the reference condition
specified by the predetermined pattern in accordance with adaptive
changes in the target levels; and the step of calculating an amount of a
difference between the signal condition detected and the reference
condition.

[0036]A recording and reproduction device for optical disk according to
the present invention includes means for reproducing data recorded on an
optical disk and detecting a predetermined pattern from the reproduced
signal; means for detecting a signal condition of the reproduced signal
that corresponds to the predetermined pattern; and means for calculating
a first recording state evaluation index value based on the detected
signal condition and a reference condition, which is specified by the
predetermined pattern and adjusted to reflect the signal condition of the
reproduced signal.

[0037]Here, when there is a plurality of the predetermined patterns, the
device may further include second calculation means for calculating a
second recording state evaluation index value using the first recording
state evaluation index value for each of the predetermined patterns.

[0038]Further, a recording and reproduction device for optical disk
according to the present invention may further include first modification
means for modifying a data recording condition for data recording based
on the second recording state evaluation index value.

[0039]Moreover, the second calculation means may calculate, for each of
the predetermined patterns, a product of an occurrence probability and
the first recording state evaluation index, and may calculate a total sum
of each of the calculated products to calculate the second recording
state evaluation index value.

[0040]Further, a recording and reproduction device for optical disk
according to the present invention may further include means for judging
whether or not the second recording state evaluation index value has
exceeded a predetermined threshold; and means for identifying the
predetermined pattern that has a predetermined or greater influence level
on the second recording state evaluation index value based on the
corresponding first recording state evaluation index value when the
second recording state evaluation index value has exceeded the
predetermined threshold.

[0041]Further, a recording and reproduction device for optical disk
according to the present invention may further include second
modification means for modifying a recoding parameter used for data
recording based on the first recording state evaluation index value
relating to the identified pattern.

[0042]A first optical information recording medium according to the
present invention stores a threshold value for a second recording state
evaluation index value that is calculated by: calculating a product of a
first recording state evaluation index value and an occurrence
probability of a predetermined pattern, the first recording state
evaluation index corresponding to a difference between signal condition
of a reproduced signal that corresponds to the predetermine pattern and a
reference condition that is specified by the predetermined pattern and
adjusted to reflect the signal condition of the reproduced signal; and by
calculating a total sum of the calculated products.

[0043]A second optical information recording medium according to the
present invention stores data representing a relation between a second
recording state evaluation index value and recording conditions for data
from which the second recording state evaluation index value is
calculated, the second recording state evaluation index value being
calculated by: calculating a product of a first recording state
evaluation index value and an occurrence probability of a predetermined
pattern, the first recording state evaluation index corresponding to a
difference between a signal condition of a reproduced signal that
corresponds to the predetermine pattern and a reference condition that is
specified by the predetermined pattern and adjusted to reflect the signal
condition of the reproduced signal; and calculating a total sum of the
calculated products.

[0044]A third optical information recording medium according to the
present invention stores data representing a relation between a recording
state evaluation index value and recording parameters for data from which
the recording state evaluation index value is calculated, the recording
state evaluation index corresponding to a difference between a signal
condition of a reproduced signal that corresponds to a predetermine
pattern and a reference condition that is specified by the predetermined
pattern and adjusted to reflect the signal condition of the reproduced
signal.

[0045]A program for causing a processor to execute the data recording
evaluation method according to the present invention may be created. The
program may be stored in, for example, an optical disk, such as a
flexible disk or CD-ROM, a magneto-optical disk, a storage medium or
storage device such as a semiconductor memory or hard disk, or a
nonvolatile memory of a processor. The program may be distributed in the
form of digital signals through a network. Data under processing may be
temporarily stored in a storage device, such as the memory of a
processor.

Advantageous Effects of the Invention

[0046]According to the present invention, it is possible to make a total
evaluation of data recording by introducing a novel evaluation index
compliant with adaptive PRML and reduce reproduction errors.

[0047]According to another aspect of the present invention, it is possible
to make an appropriate evaluation of individual record patterns by
introducing a novel evaluation index compliant with adaptive PRML and
reduce reproduction errors.

[0048]According to another aspect of the present invention, it is possible
to enable appropriate correlation between a total evaluation of data
recording and an evaluation of data recording for individual record
patterns in compliance with adaptive PRML and reduce reproduction errors.

[0049]According to another aspect of the present invention, it is possible
to make an appropriate adjustment of recording conditions or recording
parameters based on an evaluation of data recording compliant with
adaptive PRML, thus reducing reproduction errors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 is a diagram showing transitions of an amplitude level with
time.

[0051]FIG. 2 is a diagram showing the relationship between record patterns
and occurrence probabilities.

[0052]FIG. 3 is a diagram showing the relationship between effective
patterns, PRerror_ttl, and pattern effective rate.

[0053]FIG. 4 is a diagram showing the relationship between recording
power, DCJ, and PRerror_ttl.

[0054]FIG. 5 is a diagram showing the relationship between recording
power, SER, and PRerror_ttl.

[0055]FIG. 6 is a diagram showing the relationship between recording
parameter dTtop2 T, SER, and PRerror_ttl.

[0056]FIG. 7 is a diagram showing changes in PRerror_ptn(p) when a record
pattern is changed.

[0057]FIG. 8 is a diagram showing changes in PRerror_ptn(p) when a record
pattern is changed.

[0058]FIG. 9 is a diagram showing changes in PRerror_ptn(p) when a record
pattern is changed.

[0059]FIG. 10 is a diagram showing changes in PRerror_ptn(p) when a record
pattern is changed.

[0060]FIG. 11 is a diagram illustrating a target level when PR(1,2,2,1) is
used.

[0062]FIG. 13 is a diagram illustrating the calculation of a target level.

[0063]FIG. 14 is a flowchart showing the steps of an adaptive target level
setting process.

[0064]FIG. 15 is a diagram showing changes in PRerror_ptn(p) when a target
level is changed.

[0065]FIG. 16 is a diagram showing changes in PRerror_ptn(p) when a target
level is changed.

[0066]FIG. 17 is a diagram showing changes in PRerror_ptn(p) when a target
level is changed.

[0067]FIG. 18 is a diagram showing changes in PRerror_ptn(p) when a target
level is changed.

[0068]FIG. 19 is a diagram illustrating the difference in PRerror_ttl
between general PRML and adaptive PRML.

[0069]FIG. 20 is a diagram showing changes in PRerror_ptn(p) when a record
parameter is changed.

[0070]FIG. 21 is a diagram showing changes in PRerror_ptn(p) when a record
parameter is changed.

[0071]FIG. 22 is a diagram showing changes in PRerror_ptn(p) when a record
parameter is changed.

[0072]FIG. 23 is a diagram showing changes in PRerror_ptn(p) when a record
parameter is changed.

[0073]FIG. 24 is a diagram showing the relationship between dTtop2 T and
PRerror_ptn(p).

[0074]FIG. 25 is a functional block diagram of an optical recording and
reproducing system according to an embodiment of the present invention.

[0075]FIG. 26 is a flowchart showing the steps for optimizing recording
conditions before recording data.

[0076]FIG. 27 is a flowchart showing the steps of a process of calculating
PRerror_ptn(p).

[0077]FIG. 28 is a flowchart showing the steps for optimizing recording
parameters before recording data.

[0078]FIG. 29 is a flowchart showing the steps for correcting a recording
condition during data recording.

[0079]FIG. 30 is a flowchart showing the steps of a process of determining
a correction amount for a recording condition.

[0080]FIG. 31 is a flowchart showing the steps for correcting a recording
parameter during data recording.

[0081]FIG. 32 is a flowchart showing the steps of a process of determining
a correction amount for a recording parameter.

[0082]FIG. 33 is an illustration showing an example of a data structure
for storing reference data in an optical disk.

EXPLANATION OF REFERENCE NUMERALS

[0083]1: Optical Unit (PU)

[0084]3: Pre-Equalizer (Pre-EQ)

[0085]5: ADC

[0086]7: Equalizer

[0087]9: Viterbi Decoder

[0088]11: Control Unit

[0089]13: Recording Waveform Generation Unit

[0090]15: Optical Disk

[0091]17: Memory

[0092]111: Symbol Identification Section

[0093]113: Detection Instructing Section

[0094]115: Detection Section

[0095]117: Calculation Section

DESCRIPTION OF PREFERRED EMBODIMENTS

[Principle of the Present Invention]

[0096]The present invention realizes a principle of error reduction in a
reproduction system through a combination of a novel evaluation
index-based data recording evaluation method and a reference condition
adjusted so as to follow changes in a reproduction signal without any
adverse effects that exist when the signal state serving as a reference
for the evaluation index is fixed.

[0097]Hereinafter, a description will be made on an individual data
recording evaluation method (PRerror for each pattern), a data recording
evaluation method (total evaluation index PRerror_ttl) which makes a
total evaluation by putting together individual evaluations, an adjusted
reference condition which serves as a reference for comparison of the
individual data recording evaluation method, that is, setting of a target
level, and adaptive change thereof, and the relationship between the data
evaluation method and parameters.

[1] PRerror for Each Pattern

[0098]FIG. 1 shows an amplitude level of a reproduction equalization
signal which is a signal state of a corresponding detection signal when a
pattern, for example, including a mark having a length of 4 T and an
adjacent space having a length of 3 T on each side of the mark is read as
a predetermined detection pattern. In FIG. 1, the vertical axis
represents the amplitude level of the reproduction equalization signal,
and the horizontal axis represents a profile number at a channel clock
position of a data sample. When an ideal detection signal (ideal signal)
corresponding to the above-described pattern, namely PR(1,2,2,1) used in
the BD standard is used, the values for each profile number at the
channel clock position are plotted as 1, 3, 5, 6, 5, 3, 1 when converted
to an amplitude level and arranged in order. On the contrary, the signal
state of an actual detection signal depends on the hardware, an optical
disk, and recording conditions as shown in FIG. 1, and thus deviates from
an ideal state, namely a reference condition. Therefore, a gap between a
reference signal state and the signal state of the detection signal is
quantified using Equation (1) to evaluate the recording state. Based on
the evaluation, the reproduction errors are reduced by adjusting the
recording power during writing in accordance with the gap.

[0099]The signal states are expressed by equalizing a reproduction signal
of a central mark having a length of 4 T when a pattern including the 4 T
mark and an adjacent space having a length of 3 T on each side of the
central 4 T mark is read, and the signal states serve as profile values.
The influence of the adjacent symbols is the smallest at the center of
the mark, and the influence of the adjacent symbols on the left and right
ends of the mark is quantified. The reference ideal signal state refers
to a theoretical value expressed by the Viterbi algorithm. In the present
invention, it is important to change the reference signal state in
accordance with a reproduction signal rather than the theoretical value.

[0100]An evaluation of the recording state is calculated by the following
equation.

[0101]In this equation, D(x) represents the value of a detection signal,
R(x) represents the value of an amplitude level of a reference signal, x
represents a data profile number, a represents an processing beginning
data number, n represents the number of processing data sampling
(pieces), and p represents a record pattern type (number).

[0102]Similarly, in the case of a signal which is equalized to the
equalization characteristics such as PR(1,2,2,2,1) used in the HD-DVD
standard rather than PR(1,2,2,1) of the BD standard, the signal state can
be evaluated by quantifying the gap between the reference signal state
and the detection signal state. Moreover, since such a signal state is
evaluated after the signal has passed through an equalizer, the
evaluation is based on the difference between the amplitude levels of the
reproduction equalization signals equalized to the equalization
characteristics. However, describing it in terms of the signal state of
the reproduction signal has the same meaning as above.

[0103]In the above description of the present invention, an optical disk
recording method in which the quantity of reflected light at a mark is
greater than the quantity of reflected light at a space is illustrated as
an example. Such a method is referred to as a "Low-to-High" method.
However, contrary to such an example, the same evaluation can be
performed in a recording condition in which the quantity of reflected
light at a mark is smaller than the quantity of reflected light at a
space. Such a method is referred to as a "High-to-Low" method.

[0104]Further, the pattern described above is merely an example, and other
patterns can be also evaluated using Equation (1).

[0105]For example, PRerror_ptn(p) is calculated using seven points around
a peak value of the group of points where a=1 and n=7 in the equation.
Alternatively, PRerror_ptn(p) may be calculated using three points around
a peak value of the group of points where a=3 and n=3. Moreover, p is a
number which is assigned to identify a set record pattern and which is
the number of record patterns required for the evaluation. The number p
changes depending on the definition of the number of symbols arranged to
form a unit set record pattern. Moreover, although one record pattern is
formed by a "space_mark_space" pattern or a "mark_space_mark" pattern in
the example of FIG. 1, the pattern may be formed by other combinations.

[0106]That is, if a pattern has a central nT symbol which is a mark or a
space, the pattern has adjacent nT symbols which are either spaces or
marks. The pattern is a combination pattern in which, if the pattern has
a central nT symbol which is a mark, the adjacent nT symbols are spaces.
The present invention can be applied to a combination pattern in which
the spaces or marks of the adjacent nT symbols correspond to the leading
nT symbol and the trailing nT symbol.

[0107]Moreover, the present invention can be applied to a combination
pattern of four nT symbols or a combination pattern of five nT symbols.

[0108]Further, while Equation (1) shows an operation performed when a
recorded pattern p is detected once, it is desirable in practice to
obtain an average of a plurality of values (cnt(p)) by considering the
influence of variations in recording or detection. Here, the plurality of
values is about 10 thousand code data which are reproduced so as to
ensure the reliability of a combination of symbols of an intended
pattern. The average is calculated from the values of reproduction
equalization signals which are converted from respective detection
patterns obtained by the occurrence probabilities of the code data. The
number cnt(p) represents the number of detection counts of set record
patterns p obtained from sample data having a predetermined length. When
deriving the final value of PRerror_ptn(p), it is preferable to record
PRerror_ptn(p) calculated for each detection pattern in a memory as
PRerror_ptn(p, cnt(p)) and use an average of such values.

[2] Total Evaluation Index PRerror_ttl

[0109]A description will be made on a method of making a total evaluation
of a reproduction signal using the above-described PRerror_ptn(p).

[0110]The appearance frequencies of patterns p within a range of about 10
thousand code data are different, and the degrees of influence on the
recording characteristics are different. That is, the higher the
appearance frequency of a pattern, the more likely to affect the
recording characteristics. Therefore, when making a total evaluation of
recording characteristics of a reproduction signal, it is preferable to
calculate a total evaluation index PRerror_ttl which quantifies the
recording characteristics of the reproduction signal by using a
characteristic value PRerror_ptn(p) of the pattern p and the appearance
frequency, namely the occurrence probability, of the pattern p within a
predetermined range of data. Specifically, the PRerror_ttl is calculated
using the following equation.

[0111]FIG. 2 shows an example of the relationship between patterns in
about 10 thousand recorded code data and their occurrence probabilities.
In FIG. 2, the vertical axis represents the occurrence probabilities of
the entire patterns, and the horizontal axis represents the pattern types
when a row of three signs constitutes one record pattern. The first
number represents n of an adjacent leading nT symbol. The second alphabet
y represents n of the central (main) nT symbol, and the third alphabet z
represents n of an adjacent trailing nT symbol. The n values are any
number of 2 to 8 of 2 T to 8 T (9 T may be included when a synchronous
sign is included) expressed in the 1-7 PP modulation method which is used
in the BD standard. The n values have a greater value as they get closer
to the right side of FIG. 2. As will be understood from FIG. 2, a pattern
using shorter symbols has a higher occurrence probability, whereas a
pattern using longer symbols has a lower occurrence probability. For
example, when marks and spaces which are short symbols appear repeatedly,
a reproduction signal corresponding to these symbols has a small
amplitude level, which suggests a high possibility of the occurrence of
an error. This is why the present invention utilizes the concept of the
occurrence probability.

[0112]As described above, if a pattern has a high occurrence probability,
it can be said that the recording characteristics of the pattern, namely,
the magnitude of the value given by the expression of the PRerror_ptn(p)
have a great influence on the overall recording characteristics. In other
words, it can be said that a pattern having an extremely low occurrence
probability may be left out of consideration since the recording
characteristics thereof, namely the magnitude of the value give by the
expression of PRerror_ptn(p) is not so significantly reflected in the
overall recording characteristics.

[0113]Therefore, as shown in FIG. 2, total quantification of the recording
characteristics of a reproduction signal may be carried out by regarding
only patterns of which the occurrence probabilities are equal to or
greater than a predetermined occurrence probability, which serves as a
specified value, as effective patterns. In this way, it is possible to
reduce an operation load of the characteristic value while maintaining
the accuracy of a desired characteristic value (PRerror_ttl).

[0114]In FIG. 3, changes in the ratio (pattern effective rate) of the
total number of effective patterns to the total number of patterns within
a predetermined measurement range when the specified value of the
occurrence probability shown in FIG. 2 is changed are plotted along with
the values of changes in the PRerror_ttl corresponding to the ratio
changes to show the relationship between such changes. In FIG. 3, the
vertical axis on the left side represents the values of PRerror_ttl, the
vertical axis on the right side represents the pattern effective rates,
and the horizontal axis represents specified values, namely thresholds,
for effective patterns.

[0115]It can be understood from FIG. 3 that the specified value in which
the accuracy of PRerror_ttl can be ensured can be set even when patterns
of which the occurrence probabilities are smaller than the predetermined
specified value are not used for calculation of the characteristic value
PRerror_ttl. That is, according to the verification result of FIG. 3,
there is substantially no change in PRerror_ttl even when the
predetermined specified value is 0.3%. In addition, since the effective
pattern rate is about 70%, the operation load can be reduced by about
30%.

[0116]As thus described, the index PRerror_ttl for total evaluation can be
calculated with sufficient accuracy by, for example, calculating the
index PRerror_ptn(p) only for patterns having an occurrence probability
equal to or higher than 0.3% instead of calculating the index
PRerror_ptn(p) for all record patterns.

[0117]Next, changes in the PRerror_ttl when the recording power is changed
continuously are shown in FIGS. 4 and 5 together with changes in DC
jitters (hereinafter referred to as DCJ) and a symbol error rate
(hereinafter referred to as SER), which are evaluation indices currently
in use, for comparison. In FIG. 4, the vertical axis on the right side
represents DCJ [%], the vertical axis on the left side represents the
PRerror_ttl, and the horizontal axis represents a recording power PW
[mW]. In FIG. 5, the vertical axis on the right side represents SER, the
vertical axis on the left side represents the PRerror_ttl, and the
horizontal axis represents a recording power PW [mW].

[0118]It can be understood from FIGS. 4 and 5 that this evaluation value
PRerror_ttl is an index which has a high correlation with the existing
evaluation indices (DCJ and SER). Therefore, the recording
characteristics can be improved by adjusting the recording conditions in
accordance with changes in this evaluation value PRerror_ttl.
Specifically, when the PRerror_ttl can be calculated for a plurality of
recording conditions, a recording condition providing the smallest
PRerror-ttl may be adopted and set to obtain the most preferable
recording characteristics. Moreover, as will be described in detail
later, even when it is not possible to calculate the PRerror_ttl for a
plurality of recording conditions, the recording conditions can be
adjusted using PRerror_ttl which is calculated based on the results of
detection.

[0119]In the first changing step, in practice, by setting the PRerror_ttl,
which is the second evaluation index value, to a small value within a
range of equal to or smaller than a certain value by considering the data
of FIGS. 4 and 5, it is possible to maintain a high recording quality of
an optical disk. For example, in FIG. 4, if the DCJ value [%] is equal to
or lower than about 7%, it is possible to obtain an intended result.
Moreover, if the PRerror_tt value is equal to or smaller than about 0.17,
it is possible to obtain an intended result. Moreover, for example, in
FIG. 5, if the SER value is equal to or lower than about 2.0E-04, it is
possible to obtain an intended result. Furthermore, if the PRerror_tt
value is equal to or smaller than about 0.17 as described above, it is
possible to obtain an intended result.

[3] Evaluation of the Influence Level of Each Set Record Pattern on Total
Evaluation Index PRerror_ttl

[0120]Next, a description will be made on a method of evaluating the
recording state for each pattern from a comparison between the influence
levels (PRerror_ptn(p)) for each set record pattern which constitutes the
PRerror_ttl.

[0121]When a signal is written on an optical disk as symbols, the writing
is performed while controlling the intensity of a laser beam. For
example, when a mark having a length of 3 T or more among marks having a
length of an nT symbol is written with a constant width, heat control is
performed using a plurality of divided short rectangular waves rather
than using a simple rectangular wave of a laser beam, and heat may remain
at the end of the writing. When writing is performed in such a manner, a
method of performing control using a modulated waveform is referred to as
"write strategy". Moreover, the irradiation of the laser beam at the
beginning of the writing is performed while controlling the amounts of
forward and backward shifts of the beam from a reference position (0) for
a starting position (referred to as dTtop) of a top pulse so that a mark
having a length of nT can be written with a constant width from an
intended position.

[0122]FIG. 6 shows changes in the PRerror_ttl and SER when only the
central (main) symbol y after the 2 T space is changed in order to
investigate the optimal value for the amount of a shift of the starting
position of the top pulse of a 2 T mark recording pulse in a particular
strategy parameter dTtop2 T. In FIG. 6, the vertical axis on the left
side represents the PRerror_ttl, the vertical axis on the right side
represents the SER, and the horizontal axis represents the dTtop2 T. It
can be understood that both PRerror_ttl and SER change similarly to have
minimum values with changes of dTtop2 T. It can be understood that the
minimum values of PRerror_ttl and SER are both at about -1 in practice.
This value is detected and reflected in the amount of a shift of the
starting position of the top pulse (referred to as dTtop) from the
reference position.

[0123]Further, FIGS. 7 to 10 show 3-D bar graphs showing the influence
levels PRerror_ptn(p) for each pattern which constitutes the PRerror_ttl
when a correction amount of dTtop2 T is 0 in FIG. 6. FIG. 7 shows
respective PRerror_ptn(p) values obtained for a Pit_f pattern whose main
symbol is an nT mark and whose adjacent symbol is a leading nT space.
FIG. 8 shows respective PRerror_ptn(p) values obtained for a Pit_r
pattern whose main symbol is an nT mark and whose adjacent symbol is a
trailing nT space. FIG. 9 shows respective PRerror_ptn(p) values obtained
for a Land_f pattern whose main symbol is an nT space and whose adjacent
symbol is a leading nT mark. FIG. 10 shows respective PRerror_ptn(p)
values obtained for a Land_r pattern whose main symbol is an nT space and
whose adjacent symbol is a trailing nT mark.

[0124]Referring to FIGS. 7 to 10, the reason why a pattern including short
symbols such as a 2 T mark or 2 T space has a high influence level is due
to the fact that the pit for a 2 T symbol is not easily made, and is
therefore likely to deviate from a reference condition, and that a
pattern including such symbols has a high occurrence probability.

[0125]In this way, each set record pattern can be evaluated from the
PRerror_ptn(p) values which constitute the total evaluation index value
PRerror_ttl.

[0126]Due to limitations in graphical representation, FIGS. 7 to 10 show
only the influence levels of a set record pattern which is a combination
of a main symbol and an adjacent (leading or trailing) symbol on one side
thereof However, in an actual system, a pattern which is a combination of
a main symbol and adjacent (leading and trailing) symbols on both sides
thereof may be evaluated. Moreover, if necessary, a symbol which is
located further out from the adjacent leading or trailing symbol may be
included in a combination pattern.

[0127]Hereinabove, a description has been made on the individual data
recording evaluation method (PRerror for each pattern) and the data
recording evaluation method (total evaluation index PRerror_ttl) which
makes a total evaluation by putting together individual evaluations. In
these evaluations, a method of measuring the gap of a detection signal
from a fixed ideal signal serving as a reference was described. Moreover,
a description has been made on a method of adjusting the recording power
so as to minimize the errors associated with individual code patterns by
making an evaluation considering the occurrence probability and the
influence level, and a correction method of adjusting the starting
position of the top pulse of a write strategy so as to minimize the
errors by making a total evaluation by putting together individual
patterns. By such an invention, a considerably high reproduction quality
can be expected.

[0128]However, if the signal serving as the reference for the
above-described evaluation is fixed during the maximum likelihood
decoding, a situation may occur in which it is not always possible to
minimize the errors during reproduction. Therefore, it becomes important
to change the reference signal at an appropriate time in accordance with
the reproduction signal.

[0129]The present invention aims to realize high-quality reproduction,
such as minimization of errors during reproduction, by providing a
routine function in which by changing a signal serving as a reference for
an evaluation during maximum likelihood decoding in accordance with a
reproduction signal at an appropriate time, individual data recording
evaluations (PRerror for each pattern) are made based on the changed
reference signal so that a correction instruction is issued so as to
obtain an optimal reference signal corresponding to a reproduction signal
obtained by reproducing recorded data.

[0130]A description will be made of an example of a method of setting such
a reference signal by way of a method of setting a target level and the
changes in the target level with the flow of a reproduction signal.

[4] Adaptive Change of Target Level

[0131]First, general target levels will be described with reference to
FIG. 11. This description is an example when PR(1,2,2,1) used in the BD
standard is used. FIG. 11 shows symmetrical signals which are a signal
composed of a 5 T (or longer) space, a 2 T mark, and a 5 T (or longer)
space and a signal composed of a 5 T (or longer) mark, a 2 T space, and a
5 T (or longer) mark. As shown in the figure, the values of the target
levels of the respective amplitude levels during Viterbi decoding using
PR(1,2,2,1) have a 7-step level ranging from 0 to 6. These level values
at the channel clock position have a minimum level value of 0, which is
the peak level value of an amplitude level corresponding to a mark, a
maximum level value of 6, which is the peak level value of an amplitude
level corresponding to a space, and a central level value of 3. The upper
and lower level values which are the closest to the central level are 4
and 2, respectively. Moreover, the upper and lower level values which are
the second closed to the central level are 5 and 1, respectively. As
described above, the spacing between the level values in the general
target levels is equal and fixed. A judgment of the reproduction
equalization signal, which has been subjected to waveform equalization,
is made based on this target level. However, the adverse effects of
fixing the comparison reference of such an equally spaced reproduction
equalization signal are as described above. The same statements can be
applied to the case of using PR(1,2,2,2,1) used, for example, in the
HD-DVD standard as the case of the BD standard, and description thereof
will be omitted.

[0132]With reference to FIGS. 12, 13, and 14, an example of a dynamic
setting method of the target level applicable to the present invention
will be described in detail.

[0133]First, an optical recording information medium to be reproduced is
irradiated with a laser beam, and reflected light from the optical
recording information medium is received. The reflected light is
converted into an electric signal and converted into a digital signal to
generate a reproduction signal (FIG. 14: step S101). Moreover, a waveform
equalization process corresponding to PR characteristics is performed on
the generated reproduction signal (step S103). Then, symbol
identification is performed on the reproduction equalization signal which
has been subjected to waveform equalization to detect the peak level of
the reproduction equalization signal (step S105).

[0134]Specifically, in the case of an application example to the BD
standard, an average value of the peak level values in amplitude profiles
of the reproduction equalization signal corresponding to the mark and
space of the shortest symbol, an average value of the peak level values
in amplitude profiles of the reproduction equalization signal
corresponding to the mark and space of the next shortest symbol, an
average value of the peak level values in amplitude profiles of the
reproduction equalization signal corresponding to the mark and space of
the third shortest symbol, an average value of the peak level values in
amplitude profiles of the reproduction equalization signal corresponding
to the mark and space of one of the upper two symbols whose length is
twice or more longer than the shortest symbol and whose occurrence
probability in a symbol length in which the signal amplitude reaches a
saturation state is high, and an average value of the peak level values
in amplitude profiles of the reproduction equalization signal
corresponding to the mark and space of a symbol having a length of 5 T or
longer are detected as the respective peak level values.

[0135]Moreover, in the case of the HD-DVD standard, an average value of
the peak level values of a signal corresponding to the mark and space of
the shortest symbol, an average value of the peak level values of a
signal corresponding to the mark and space of the next shortest symbol,
an average value of the peak level values of a signal corresponding to
the mark and space of the third shortest symbol, an average value of the
peak level values of a signal corresponding to the mark and space of one
of the upper two symbols whose length is twice as long as the shortest
symbol and whose occurrence probability is high, and an average value of
the peak level values of a signal corresponding to the mark and space of
a symbol having a length of 5 T or longer are detected as the respective
peak levels.

[0136]Moreover, the target levels of the signals used during the Viterbi
decoding are determined based on the relative positional relationship
between the detected peak level values, and are set in a processor that
performs Viterbi decoding processing (step S107). Hereinafter, the
contents of this step will be described in detail.

(1) Central Level of All Target Levels of Signals Used for Viterbi
Decoding

[0137]In the case of PR(1,2,2,1), the central level value is around 3.

[0138]Moreover, in the case of PR(1,2,2,2,1), the central level value is
around 4.

[0139]The peak level values A and B corresponding to the mark and space,
respectively, of a symbol having a length of 5 T or longer are detected.
Next, the peak level value C corresponding to a mark of the shortest
symbol is detected. At the same time, the peak level value D
corresponding to a space of the shortest symbol is detected. Thereafter,
an intermediate level value E of the values C and D is computed. A value
that is calculated by a relative value through computation from the three
values A, B, and E thus obtained is set as the central level value.

[0140]Here, instead of the symbol having a length of 5 T or longer, at
least one of the two highest occurring symbols in terms of occurrence
probabilities among the symbols that have a length twice or more longer
than the shortest symbol and that have the signal amplitude reaching a
saturation state can be used. The peak level values of the signal
corresponding to the mark and space of such a symbol can be substituted
for the values A and B of the peak level values of the signal
corresponding to the symbol having a length of 5 T or longer. The same
substitution can be applied in the following cases, and description
thereof will be omitted.

[0141]In the case of PR(1,2,2,1), the level values are around 2 and 4,
respectively.

[0142]In the case of PR(1,2,2,2,1), the level values are around 3 and 5,
respectively.

[0143]The peak level values A and B of a signal corresponding to the mark
and space of a symbol having a length of 5 T or longer are detected.
Next, the peak level value D of a signal corresponding to a mark of the
shortest symbol is detected. Further, the values A and B and the peak
level value C are detected. At the same time, the peak level value C of a
signal corresponding to a space of the shortest symbol is detected.
Thereafter, a value that is calculated by a relative value through
computation from the three values A, B, and C thus obtained is set as the
level value that is located the closest to the central level of the
target levels for the mark used for the Viterbi decoding. At the same
time, a value that is calculated by a relative value through computation
from the three values A, B, and D is calculated and set as the level
value that is located the closest to the central level of the target
levels for the space used for the Viterbi decoding.

[0144]The relationship between the mark and space changes its polarity
depending on the recording method (High-to-Low/Low-to-High). In the case
of High-to-Low, the lower levels are determined using the peak level of
the mark of the shortest symbol, and the upper levels are determined
using the peak level of the space of the shortest symbol. In the case of
the Low-to-High, the levels are determined in an opposite manner. In the
following description, this relationship between the mark and space and
the recording method remains the same. In the description of the present
invention, an example of using the Low-to-High method is described.
Therefore, although description of the High-to-Low method is omitted, the
same can be understood by changing the polarities.

(3) Levels Corresponding to 3 T Mark and 3 T Space Located Second Closest
to Central Level of Target Level

[0145]In the case of PR(1,2,2,1), the level values are around 1 and 5,
respectively.

[0146]In the case of the characteristics of PR(1,2,2,2,1), the level
values are around 2 and 6, respectively.

[0147]The peak level values A and B of a signal corresponding to the mark
and space of a symbol having a length of 5 T or longer are detected.
Next, the peak level value F of a signal corresponding to a mark of the
second shortest symbol is detected. At the same time, the peak level
value G of a signal corresponding to a space of the second shortest
symbol is detected. Thereafter, a value that is calculated by a relative
value through computation from the three values A, B, and F thus obtained
is set as the level value that is located the second closest to the
central level of the target levels for the mark used for the Viterbi
decoding. At the same time, a value that is calculated by a relative
value through computation from the three values A, B, and G is calculated
and set as the level value that is located the second closest to the
central level of the target levels for the space used for the Viterbi
decoding.

(4) Levels Corresponding to 4 T Mark and 4 T Space Located Third Closest
to Central Level of Target Level

[0148]In the case of the characteristics of PR(1,2,2,1), the level values
are around 0 and 6, respectively.

[0149]In the case of the characteristics of PR(1,2,2,2,1), the general
level values are around 1 and 7, respectively.

[0150]The peak level values A and B of a signal corresponding to the mark
and space, respectively, of a symbol having a length of 5 T or longer are
detected. Next, the peak level value H of a signal corresponding to a
mark of the third shortest symbol is detected. At the same time, the peak
level value I of a signal corresponding to a space of the third shortest
symbol is detected. Thereafter, a value which is calculated by a relative
value through computation from the three values A, B, and H thus obtained
is set as the level value that is located the third closest to the
central level of the target levels for the mark used for the Viterbi
decoding. At the same time, a value which is calculated by a relative
value through computation from the three values A, B, and I is calculated
and set as the level value that is located the third closest to the
central level of the target levels for the space used for the Viterbi
decoding.

(5) Maximum and Minimum Levels of Target Level

[0151]In the case of the characteristics of PR(1,2,2,1), the level values
of a signal corresponding to a symbol having a length of 5 T or longer
are 0 and 6. Therefore, the level values of the two highest occurring
symbols in terms of occurrence probability among the symbols that have a
length twice or more longer than the shortest symbol and that have the
signal amplitude reaching a saturation state are substantially the same
as the level values of a symbol having a length of 5 T or longer. In this
case, substantially the same results are obtained regardless of which
level value is used.

[0152]In the case of the characteristics of PR(1,2,2,2,1), the level
values are 0 and 8, respectively.

[0153]The peak levels of the mark and space of at least one of the two
highest occurring symbols in terms of occurrence probability among the
symbols that have a length more than twice longer than the shortest
symbol are determined as the maximum and minimum level values of the
target levels used for the Viterbi decoding. Which one of the mark and
space will correspond to the maximum and minimum levels is determined
depending on the recording method similar to the above-described
examples.

[0154]Instead of using the calculated peak level values as the target
levels as described above, values obtained by multiplying the peak level
values with an appropriate coefficient may be used as the target level
values. Moreover, in the case of the PR(1,2,2,1), any one of the above
described (4) and (5) may be used.

[0155]By performing the above-described process, the target levels which
were arranged at equal spacings in the related-art technique are arranged
at non-equal spacings by computing the relative values in accordance with
the actual state of the peak levels.

[0156]A specific example of setting target levels for the case of the BD
standard is shown in FIGS. 12 and 13. A relative intermediate level value
of the peak level of a 2 T mark and the peak level of a 2 T space is set
to a target level "2.858" which is the central level so as to be shifted
toward the negative side by an amount of 0.142 as compared to the normal
case.

[0157]Further, a relative peak level value corresponding to a 2 T space is
set to a target level "2.205" so as to be shifted toward the positive
side by an amount of 0.205 as compared to the normal case. Moreover, a
relative peak level value corresponding to a 2 T mark is set to a target
level "3.511" so as to be shifted toward the negative side by an amount
of 0.489 as compared to the normal case.

[0158]Furthermore, a relative peak level value corresponding to a 3 T
space is set to a target level "1.570" so as to be shifted toward the
positive side by an amount of 0.570 as compared to the normal case.
Moreover, a relative peak level value corresponding to a 3 T mark is set
to a target level "4.222" so as to be shifted toward the negative side by
an amount of 0.778 as compared to the normal case.

[0159]In the case of a 4 T symbol, the target levels became 0 and 6 which
are the same values as a symbol having a length of 5 T or longer. By
setting the target levels in such a manner, the reduction percentage of
the error rate for a reference value was 56%.

[0160]In this way, the respective target level values are as shown in
FIGS. 12 and 13. As shown in the figures, although the target levels "6"
and "0" are fixed, the other target level values are arrange at non-equal
spacings. In this way, by controlling the arrangement of spacings using
the reproduction equalization signal in the flow of symbols from a 2 T
symbol to a symbol having a length of 5 T or longer, the target level
values used for the Viterbi decoding are obtained. As described above, by
changing the level settings of a symbol whose appearance frequency is
high and whose error rate tends to be high, it is possible to effectively
reduce the error rate for subsequent reproduction.

[0161]As a premise of the present invention, there is a technique of
adaptively changing the target signal level used for Viterbi decoding in
accordance with a reproduction equalization signal that has been
subjected to waveform equalization to reduce the error rate during
reproduction and enabling stable reproduction of information from an
optical disk.

[0162]As a method for adaptively changing the target levels in such a
manner, although the method which will be described later may be used,
other methods such as a target signal level setting method as disclosed,
for example, in JP-A-2005-346897 are known. The present invention can be
applied using such a method.

[0163]Regardless of which method is used for adaptively changing the
target levels, when the target levels are changed, the signal waveform
itself of the reproduction equalization signal serving as the reference
will be changed.

[0164]For example, when a pattern having a mark having a length of 4 T and
an adjacent space having a length of 3 T on both sides thereof is read as
described above, the amplitude level of an ideal reproduction signal has
level values of an amplitude profile which are 1, 3, 5, 6, 5, 3, 1 in the
case of using the PR(1,2,2,1) used in the BD standard. In contrast, the
target levels used in the present invention forms a signal which passes
through amplitude levels which are 0, 1.570, 2.205, 2.858, 3.511, 4.222,
and 6 as shown in FIG. 13. By changing the level values of such an
amplitude profile in accordance with the flow of a reproduction signal,
it is possible to achieve optimal quality reproduction. Moreover, by
making evaluations, the adaptive change method can be applied to the
adjustment of the recording power at the time of writing and the
adjustment of the write strategy.

[0165]By applying the technique of adaptively changing the target levels
in accordance with the reproduction signal state and then calculating the
influence levels (PRerror_ptn(p)) for each pattern constituting the
PRerror_ttl when the correction amount for the dTtop2 T is 0, the results
shown in FIGS. 15 to 18 corresponding to FIGS. 7 to 10, respectively, can
be obtained. As will be understood from FIGS. 15 to 18, the
PRerror_ptn(p) values are apparently decreased. This means that by the
adaptive change of the target levels in accordance with the reproduction
signal state, the reproduction equalization signal serving as a reference
is changed, and a gap between the detected reproduction equalization
signal and the reference reproduction equalization signal is reduced,
whereby the stability of data decoding is improved.

[0166]The PRerror_ttl values are also improved due to the fact that the
target levels are adaptively changed in accordance with the state of a
reproduction signal. FIG. 19 shows changes in PRerror_ttl in response to
a change in the recording power Pw when general PRML is used and when
adaptive PRML is used, namely when the present invention is applied. In
FIG. 19, the vertical axis represents PRerror_ttl, and the horizontal
axis represents the recording power Pw. As described above, the
PRerror_ttl values are improved as a whole. This is because the
respective PRerror_ptn(p) values that constitute the PRerror_ttl are
reduced.

[5] Relationship Between PRerror_ptn(p) and Strategy Parameter

[0167]Next, a description will be made on changes in the influence levels
(PRerror_ptn(p)) for each pattern when dTtop2 T is continuously changed
(from -2 to +1). FIGS. 20 to 23 show 3-D bar graphs for Pit_f patterns
(whose main symbol is an nT mark and whose adjacent symbol is a leading
nT space) which are greatly influenced by the change in dTtop2 T.

[0168]It can be understood from FIGS. 20 to 23 that the change in dTtop2 T
has a significant influence on the PRerror_ptn(p) corresponding to a
pattern having a 2 T space followed by a 2 T mark. In particular, the
PRerror_ptn(p) is increased greatly particularly when dTtop2 T is -2
(FIG. 20).

[0169]Next, FIG. 24 shows changes in PRerror_ptn(p) of a pattern having a
2 T space followed by a 2 T mark resulting from the change in the
recording parameter dTtop2 T. In FIG. 24, the vertical axis represents
PRerror_ptn(p), and the horizontal axis represents dTtop2 T. Moreover,
the rhombic points represent actually calculated values, and the curve
represents the result of quadratic regression of the actually calculated
values. The use of such data enables the optimization or adjustment of
the recording parameter dTtop2 T using the PRerror_ptn(p).

[0170]Although the recording parameter dTtop2 T is varied in the
above-described example, it is obvious that the same can be applied to
various recording parameters. Although FIGS. 20 to 23 show changes in the
influence levels of patterns which are combinations of a leading space
and a trailing mark, the selection of the patterns is determined in
accordance with the recording parameter used. When it is judged that the
PRerror_ptn(p) of a particular pattern has a great value which needs to
be adjusted, a corresponding recording parameter which should be adjusted
is also identified.

Embodiments

[0171]Hereinafter, embodiments for carrying out the present invention will
be described with reference to flowcharts in conjunction with the
functions of blocks of a functional block diagram of a recording and
reproduction device for optical disk.

[0172]FIG. 25 shows a functional block diagram of an optical recording and
reproduction system according to an embodiment of the present invention.
The optical recording and reproduction system according to the present
embodiment includes an optical unit (PU) 1 for irradiating an optical
disk 15 with a laser beam to perform recording or reproduction, a
pre-equalizer (Pre-EQ) 3 for performing a waveform equalizing process on
an electric signal from a photo-detector included in the optical unit 1
to facilitate the conversion of the electric signal into a digital signal
at a subsequent step, an analog/digital converter (hereinafter referred
to as "ADC") 5 for converting an analog signal into a digital signal, an
equalizer 7 for equalizing imperfect frequency response of a digital
signal having inter-symbol interference so that an amplitude level at the
central position in the length direction of an nT mark corresponds to a
peak value, and the values of the amplitude levels at positions apart
from the central position under the influence of adjacent nT spaces are
equalized to a ratio of seven levels from 0 to 6, for example, a Viterbi
decoder 9 for decoding most probable standard symbol series from
reproduction RF signals which have been subjected to waveform
equalization by the equalizer 7, a control unit 11 for performing
processing using the outputs from the equalizer 7 and the Viterbi decoder
9, a recording waveform generation unit 13 for generating a recording
waveform for write data according to setting output from the control unit
11 and outputting the recording waveform to the optical unit 1, and a
memory 17 for storing the results of the processing by the control unit
11. Although not shown, the optical recording and reproduction system may
be connected to a display device or a personal computer. In some
occasions, the system may be connected to a network to communicate with
one or a plurality of computers.

[0173]The control unit 11 includes a symbol identification section 111 for
correlating a reproduced RF signal which is the output of the equalizer 7
with maximum likelihood decoding sign data which is the output of the
Viterbi decoder 9, a detection instructing section 113 for instructing
detection of an amplitude level when an occurrence of a predetermined
detection pattern is detected based on code data from the symbol
identification section 111, a detection section 115 for detecting the
amplitude level of the reproduced RF signal from the symbol
identification section 111 in accordance with the instruction from the
detection instructing section 113, and a calculation section 117 for
calculating a peak level based on the output from the detection section
115, for performing calculation of a plurality of target levels for the
above-mentioned signal used for maximum likelihood decoding of the
reproduction signal and setting to the Viterbi decoder 9, and for
performing the operations described in the Principle of Invention
section, and adjustment and setting of strategy, and the like. Moreover,
for example, the calculation section 117 may be realized as a combination
of programs for carrying out functions described below, and a processor.
In such a case, the programs may be stored in a memory included in the
processor.

[0174]Next, a description will be made on the contents of processes
performed by the optical recording and reproduction system with reference
to FIGS. 26 to 32. First, a description will be made on a recording
condition optimization process using a trial writing area provided at the
innermost circumference of an optical disk 15 prior to data recording.

[0175]For example, the calculation section 117 of the control unit 11 sets
a predetermined recording condition in the recording waveform generation
unit 13 (FIG. 26: step S1). The recording waveform generation unit 13
writes a predetermined record pattern in the trial writing area of the
optical disk 15 using the PU 1 in accordance with the set recording
condition (step S3). Then, a PRerror_ptn(p) calculation process is
performed (step S5). The PRerror_ptn(p) calculation process will be
described with reference to FIG. 27.

[0176]First, a reproduction signal which has been subjected to waveform
equalization is generated by the PU 1, the pre-equalizer 3, and the
equalizer 7 (FIG. 27: S501), and write codes are decoded by the Viterbi
decoder 9. Moreover, the symbol identification section 111 correlates the
output of the equalizer 7 with the output of the Viterbi decoder 9. The
detection instructing section 113 instructs the detection section 115 to
detect the amplitude levels of the reproduction signals for all detection
patterns (detected strings of symbols [T]). Since the detection patterns
are used for both adaptive change of the target level and calculation of
PRerror_ptn(p), only effective patterns described above may be detected
if it is possible to perform adaptive change of the target level using
only the effective patterns.

[0177]The detection section 115 detects the amplitude levels of the
reproduced RF signal in accordance with the instruction from the
detection instructing section 113 and outputs the detection results to
the calculation section 117. Moreover, the calculation section 117
performs a predetermined operation based on the detection results of the
detection section 115 to perform adaptive change of the target level
(step S503) and sets the changed target level to the Viterbi decoder 9.
As for the processing for adaptive change of the target level, the method
described in detail above is used. However, the method is not limited to
this, and the adaptive change of the target level can be performed using
other methods. Moreover, the calculation section 117 calculates
PRerror_ptn(p) for each pattern and stores the PRerror_ptn(p) in a
storage such as a memory (step S505). As described above, since the
predetermined pattern p is detected many times, an average value of
PRerror_ptn(p) values is calculated. Moreover, the calculation section
117 stores the amplitude level of a particular pattern pc which will
be used later. Alternatively, only a peak value may be stored.

[0178]Returning to FIG. 26, the calculation section 117 calculates
PRerror_ttl using the PRerror_ptn(p) calculated for each pattern in step
S5 and the occurrence probability of each pattern stored in advance in a
memory and stores the PRerror_ttl in a storage device such as a memory as
corresponding to the recording condition set in step S1 (step S7). The
data is also used for adjusting a recording condition during data
recording.

[0179]Moreover, the calculation section 117 judges whether or not all the
predetermined recording conditions have been set (step S9), and if there
is any unset recording condition, the process returns to step S1. If
setting has been completed for all the predetermined recording
conditions, a recording condition under which the PRerror_ttl has the
smallest value is identified as an optimal recording condition based on
the PRerror_ttl for each recording condition (step S11). For example,
since recording power or the like at which the PRerror_ttl has the
smallest value can be identified, that recording power or the like is
adopted.

[0180]Moreover, the calculation section 117 sets the optimal recording
condition in the recording waveform generation unit 13 (step S13). The
amplitude level corresponding to the particular pattern pc in the
optimal recording condition is stored in a storage device such as a
memory as a reference signal (step S15). The data is used for adjusting a
recording condition during data recording.

[0181]By performing such a process, it is possible to perform a recording
condition optimization process using the trial write area based on the
PRerror_ttl and set an optimal recording condition.

[0182]Next, a case of using PRerror_ptn(p) for individual patterns will be
described as a second example of a recording condition optimization
process in the trial write area.

[0183]For example, the calculation section 117 of the control unit 11 sets
a predetermined recording parameter in the recording waveform generation
unit 13 (FIG. 28: step S21). Moreover, the recording waveform generation
unit 13 writes a predetermined pattern in the trial writing area of the
optical disk 15 using the PU 1 in accordance with the set recording
parameter (step S23). Next, PRerror_ptn(p) calculation process is
performed (step S25). This process is the same as the process described
with reference to FIG. 27. The calculated PRerror_ptn(p) values are
stored in the memory 17 as corresponding to the recording parameter set
in step S21. This data is used for adjusting the recording parameter
during data recording. As described above, since the pattern p is
detected many times, an average value of the PRerror_ptn(p) values is
calculated. Moreover, the calculation section 117 stores the amplitude
level of the pattern p. Alternatively, only a peak value may be stored.

[0184]Moreover, the calculation section 117 judges whether all
predetermined values of the recording parameter have been set (step S27),
and if there is any unset recording condition, the process returns to
step S21. If setting has been completed for all the predetermined values
of the recording parameter, the calculation section 117 identifies the
value of the recording parameter at which the PRerror_ptn(p) has the
smallest value as an optimal value based on the PRerror_ptn(p) values for
the respective values of the recording parameter (step S29). As described
above, since each detection pattern has a corresponding recording
parameter, an optimal value is identified for the corresponding recording
parameter in step S29. For example, as shown in FIG. 24, since the value
(-1) of dTtop2 T at which the PRerror_ptn(p) for a pattern p having a 2 T
space followed by a 2 T mark is smallest can be identified, that value of
dTtop2 T is adopted.

[0185]Moreover, the calculation section 117 sets the identified optimal
value in the recording waveform generation unit 13 (step S31). Moreover,
the amplitude level of the pattern p at the optimal value is stored in a
storage device such as a memory as a reference signal (step S33). The
data is used for adjusting the recording parameter during data recording.

[0186]By performing such a process, it is possible to perform a recording
parameter optimization process using the trial write area based on the
PRerror_ptn(p) and optimize at least a part of the recording parameters.

[0187]Next, a description will be made on a first example of a process of
adjusting recording conditions after data recording is started with
reference to FIGS. 29 and 30.

[0188]The recording waveform generation unit 13 writes data to be written
using the PU 1 in accordance with recording conditions set therein (step
S41). Here, it will be assumed that data are written in a predetermined
amount or for a predetermined period of time. Next, a PRerror_ptn(p)
calculation process is performed (step S45). In this example, the same
process as that described with reference to FIG. 27 is performed. The
calculated PRerror_ptn(p) values for each pattern are stored in the
memory 17. As described above, since the pattern p is detected many
times, an average value of the PRerror_ptn(p) values is calculated.
Moreover, the calculation section 117 stores the amplitude level of the
amplitude profile for a particular pattern pc which will be used
later. Alternatively, only a peak value may be stored.

[0189]Thereafter, the calculation section 117 calculates PRerror_ttl using
the PRerror_ptn(p) for each pattern calculated in step S45 and the
occurrence probability of each pattern stored in advance in a memory and
stores the calculated PRerror_ttl in the memory 17 (step S47).

[0190]Then, the calculation section 117 judges whether or not the
PRerror_ttl has exceeded a predetermined threshold (step S49). When the
PRerror_ttl is smaller than the predetermined threshold, the process
proceeds to step S55 since it is not necessary to adjust the recording
conditions. On the other hand, when the PRerror_ttl has exceeded the
predetermined threshold, the calculation section 117 performs a recording
condition correction amount determining process based on the PRerror_ttl
(step S51).

[0191]The recording condition correction amount determining process will
be described with reference to FIG. 30. First, the calculation section
117 calculates a difference between the amplitude level of an amplitude
profile for the particular pattern pc and, for example, the
amplitude level of a reference signal that is identified in step S15
(step S61). As described above, the difference between the peak values
may be calculated, or alternatively, differences between values other
than the peak values may be added. Since it has been determined in step
S49 that the PRerror_ttl has exceeded the predetermined threshold, the
difference between the amplitude level and the amplitude level of the
reference signal will not be 0 (see FIG. 1).

[0192]The calculation section 117 judges whether or not the difference is
positive (step S63). If the difference is positive, a recording condition
which results in a positive difference and which corresponds to the
PRerror_ttl value calculated in step S47 is identified (step S65) from
the relationship between the PRerror_ttl and the recording conditions
(the result of step S7). In the case shown in FIG. 4, the PRerror_ttl
value reaches its smallest at the recording power of 3.3 mW and increases
regardless of whether the recording power increases or decreases.
Therefore, when the PRerror_ttl value calculated in step S47 is 0.015,
for example, the corresponding recording power is about 3.1 mW or about
3.7 mW. The direction and the amount of correction depend on the value of
the recording power. If the recording power is 3.1 mW, it should be
increased by 0.2 mW. If the recording power is 3.7 mW, it should be
decreased by 0.4 mW. Whether the recording power will be increased or
decreased is determined by at least one condition among the
characteristics of an optical disk under data recording, the recording
condition, and the detection pattern. For example, whether an optical
disk is an optical disk in which the amplitude level will be increased in
response to an increase in the recording power or an optical disk in
which the amplitude level will be decreased in response to an increase in
the recording power is determined based on a type identification code
recorded in advance in the optical disk. For example, when the amplitude
level is increased in response to an increase in the recording power, and
the difference is positive, it can be judged that the recording power is
too high or in the state of being about 3.7 mW. Therefore, the recording
power is decreased by about 0.4 mW. On the other hand, when the amplitude
level is decreased in response to an increase in the recording power, and
the difference is positive, it can be judged that the recording power is
too low or in the state of being about 3.1 mW. Therefore, the recording
power is increased by about 0.2 mW. Such a determination may be made
based on the result of determination which is actually made at the time
of test recording instead of the type identification code. Such
relationships are identified in advance, and appropriate recording
conditions are identified in step S65.

[0193]The calculation section 117 calculates the difference between the
identified recording condition and the optimal recording condition as a
correction amount (step S69), and the process returns to the initial
step.

[0194]On the other hand, if the difference is negative, a recording
condition which corresponds to the PRerror_ttl value calculated in step
S47 is identified (step S67) from the relationship between the
PRerror_ttl and the recording conditions. For example, when it is judged
from the type identification code of the optical disk that the amplitude
level is increased in response to an increase in the recording power, and
the difference is negative, it can be judged that the recording power is
too low or in the state of being about 3.1 mW. Therefore, the recording
power is increased by about 0.2 mW. On the other hand, when it is
determined from the type identification code of the optical disk that the
amplitude level is decreased in response to an increase in the recording
power, and the difference is negative, it can be judged that the
recording power is too high or in the state of being about 3.7 mW.
Therefore, the recording power is decreased by about 0.4 mW. Such
relationships are identified in advance, and appropriate recording
conditions are identified in step S67. Then, the process proceeds to step
S69.

[0195]Returning to FIG. 29, the calculation section 117 sets the
correction amount for the recording condition determined in step S51 in
the recording waveform generation unit 13 (step S53). Then, it is judged
whether or not data recording has been completed (step S55), and the
process returns to step S41 if data recording has not been completed. On
the other hand, if data recording has been completed, the process ends.

[0196]By performing the above-described process, it is possible to adjust
the recording conditions even during data recording.

[0197]Next, a process of correcting the recording parameter based on the
PRerror_ptn(p) will be described with reference to FIGS. 31 and 32.

[0198]The recording waveform generation unit 13 writes data to be written
using the PU 1 in accordance with recording conditions set therein (FIG.
31: step S71). Here, it will be assumed that data are written in a
predetermined amount or for a predetermined period of time. Next, a
PRerror_ptn(p) calculation process is performed (step S73). As for this
process, the process shown in FIG. 27 is performed. The PRerror_ptn(p)
for each detection pattern is calculated and stored in the memory 17. As
described above, since the pattern p is detected many times, an average
value of PRerror_ptn(p) values is calculated. Moreover, the calculation
section 117 stores the amplitude level of a particular pattern pc
which will be used later. Alternatively, only the peak value of the
amplitude level may be stored.

[0199]Thereafter, the calculation section 117 calculates PRerror_ttl using
the PRerror_ptn(p) calculated for each pattern in step S73 and the
occurrence probability of each pattern stored in advance in a memory and
stores the PRerror_ttl in a storage device such as a memory (step S75).

[0200]Then, the calculation section 117 judges whether or not the
PRerror_ttl has exceeded a predetermined threshold (step S77). When the
PRerror_ttl is smaller than the predetermined threshold, the process
proceeds to step S87 since it is not necessary to adjust the recording
conditions. On the other hand, when the PRerror_ttl has exceeded the
predetermined threshold, the calculation section 117 identifies
PRerror_ptn(p) which has exceeded a predetermined threshold (step S79).
Alternatively, a predetermined number of the upper PRerror_ptn(p) values
may be identified instead of identifying the PRerror_ptn(p) which has
exceeded the predetermined threshold. Then, the recording parameters
corresponding to the pattern p correlated with the identified
PRerror_ptn(p) values are identified (step S81). For example, in the case
of a pattern having a 2 T space followed by a 2 T mark, the pattern may
be stored in advance in a memory in correlation with the pattern ID such
as dTtop2 T, and such correlation may be used for the identification.

[0202]The recording parameter correction amount determining process will
be described with reference to FIG. 32. First, the calculation section
117 calculates a difference between the amplitude level of the particular
pattern pc and the amplitude level of, for example, a reference
signal that is identified in step S33 (step S91). As described above, the
difference between the peak values may be calculated, or alternatively,
differences between values other than the peak values may be added. Since
it has been determined in step S77 that the PRerror_ttl has exceeded the
predetermined threshold, the difference between the amplitude level and
the reference signal will not be 0.

[0203]The calculation section 117 judges whether or not the difference is
positive (step S93). If the difference is positive, the value of a
recording parameter which results in a positive difference and which
corresponds to the PRerror_ptn(p) value identified in step S79 is
identified (step S95) from the relationship between the PRerror_ptn(p)
and the recording parameters (the result of step S25). In the case shown
in FIG. 24, the PRerror_ptn(p) value reaches its smallest at the dTtop2 T
of about 0 and increases regardless of whether the dTtop2 T decreases or
increases. Therefore, when the PRerror_ptn(p) value calculated in step
S73 is 0.005, for example, the corresponding dTtop2 T is about -1 or
about 0.95. The direction and the amount of correction depend on the
value of the dTtop2 T. If the dTtop2 T is -1, it should be increased by
1. If the dTtop2 T is 0.95, it should be decreased by 0.95. Whether the
dTtop2 T will be increased or decreased is determined by at least one
condition among the characteristics of an optical disk under data
recording, the recording condition, and the detection pattern. The
characteristics of the optical disk are preferably determined as follows.
For example, the amplitude level of a pattern p is stored for each value
of the recording parameter in step S25. It is determined whether the
amplitude level increases or decreases in response to an increase in the
recording parameter by executing step S25 several times, and the
determination results are used. For example, when it is judged from the
determination results that the amplitude level is increased in response
to an increase in the dTtop2 T, and the difference is positive, it can be
judged that the dTtop2 T is too large or in the state of being 0.95.
Therefore, the dTtop2 T is decreased by 0.95. On the other hand, when it
is judged from the determination results that the amplitude level is
decreased in response to an increase in the dTtop2 T, and the difference
is positive, it can be judged that the dTtop2 T is too small or in the
state of being about -1. Therefore, the dTtop2 T is increased by 1. Such
relationships are identified in advance, and appropriate recording
conditions are identified in step S95.

[0204]The calculation section 117 calculates the difference between the
identified recording parameter value and the optimal recording parameter
value as a correction amount (step S99), and the process returns to the
initial step.

[0205]On the other hand, if the difference is negative, a recording
parameter value which results in a negative difference and which
corresponds to the value of the PRerror_ptn(p) is identified (step S97)
from the relationship between the PRerror_ptn(p) and the recording
parameters. For example, when it is judged from the results of the
advance determination that the amplitude level is increased in response
to an increase in the dTtop2 T and the difference is negative, it can be
judged that the dTtop2 T is too small or in the state of being about -1.
Therefore, the dTtop2 T is increased by about 0.9. On the other hand,
when it is judged from the results of the advance determination that the
amplitude level is decreased in response to an increase in the dTtop2 T
and the difference is negative, it can be judged that the dTtop2 T is too
high or in the state of being about 0.7. Therefore, the dTtop2 T is
decreased by about 0.8. Such relationships are identified in advance, and
appropriate recording conditions are identified in step S97. Then, the
process proceeds to step S99.

[0206]Returning to FIG. 31, the calculation section 117 sets the
correction amount for the recording parameter determined in step S83 in
the recording waveform generation unit 13 (step S85). Then, it is judged
whether or not data recording has been completed (step S87), and the
process returns to step S71 if data recording has not been completed. On
the other hand, if data recording has been completed, the process ends.

[0207]By performing the above-described process, it is possible to adjust
the recording parameters even during data recording.

[0208]While it has been described for an example in which the value of the
reference signal in the processing flows shown in FIG. 30 or 32 and the
relationship between the PRerror_ttl and the recording conditions and the
relationship between the PRerror_ptn(p) and the recording parameters
shown in FIGS. 4 and 24 are acquired through the processing flow shown in
FIG. 26 or 28, such values or relationships may be stored in a memory in
advance. When the optical recording and reproducing system is connected
to a network, such data may be acquired from another computer storing the
data. Further, the processing flow shown in FIG. 26 or 28 may include a
step for correcting or updating data stored in a memory in advance.

[0209]Moreover, although FIG. 30 or 32 shows a case in which data
recording is temporarily interrupted, the recording conditions or the
recording parameters may be adjusted concurrently with data recording.

[0210]Furthermore, although FIGS. 26 and 28 show examples in which data
are reproduced after the data are recorded in accordance with one
recording condition and the data are reproduced again after the data are
recorded in accordance with another recording condition, data may be
reproduced after the data are recorded in accordance with all recording
conditions.

[0211]Other processing flows may be modified as necessary.

[0212]Although the embodiments of the present invention have been
described above, the present invention is not limited to the embodiments.
For example, the functional block diagram of the optical recording and
reproducing system shown in FIG. 25 is merely an example, and the present
invention is not limited to the configuration of functional blocks shown
in FIG. 25 as long as the above-described functions can be realized.

[0213]In addition, although the above description has been made on an
example in which the dTtop2 T is adjusted, if it is necessary to adjust a
trailing space conversely, a parameter Tlp of a trailing edge of a
recording pulse may be adjusted. In this way, an appropriate recording
parameter is identified and adjusted in accordance with a detection
pattern.

[0214]Although in the above embodiments have been described for an example
in which reference data such as thresholds used for adjusting the
recording conditions or the like during data recording are stored in a
memory incorporated in the calculation section 117 or an external memory
connected to the calculation section 117, it is not always necessary to
store such data in a memory. For example, the data may be stored in the
optical disk 15. When the data are stored in the optical disk 15, the
data may be stored in a lead-in region as shown in FIG. 33. The lead-in
region is roughly divided into a system lead-in area, a connection area,
and a data Lead-in area. The system lead-in area includes an initial
zone, a buffer zone, a control data zone, and another buffer zone. The
connection area includes a connection zone. The data lead-in area
includes a guard track zone, a disk test zone, a drive test zone, another
guard track zone, an RMD duplication zone, a recording management zone,
an R-physical format information zone, and a reference code zone. In the
present embodiment, the control data zone of the system lead-in area
includes a recording condition data zone 170.

[0215]The reference data to be stored in a memory are stored in the
recording condition data zone 170 and are read at an appropriate time.
Regarding the values to be recorded, the average values of the optical
disk 15 may be stored. Alternatively, values measured by tests performed
on the optical disk 15 prior to shipment may be registered.

[0216]By storing the values corresponding to the optical disk 15, on which
recording is to be performed, in the optical disk 15, processing loads on
the drive side can be reduced. The values stored in the optical disk 15
may be corrected and used if necessary.

[0217]By setting the values calculated in the above-described manner to a
processor performing Viterbi decoding, a reduction in the symbol error
rate of symbol identification during later reproduction is expected.